1. Field of the Invention
The present invention relates to a process for ameliorating or preventing diseases that are caused, in part, by an increased level of, and/or an abnormal responsivity to, interferon. Alzheimer's disease, HIV infection, Down syndrome, transplant rejection, autoimmune disease, and infant encephalitis are examples of such diseases. Specifically, the invention provides a method for treating subjects suffering from, or at risk for, such diseases by the administration of a pharmacological preparation of interferon binding proteins of mammalian and/or viral origin that antagonize interferon's action. This invention comprises compositions of interferon binding proteins that can inhibit the activity of interferon gamma plus interferon alpha such compositions along with their method of production and modification being described herein.
2. Background of the Invention
The Molecular Biology of Interferons and Interferon Receptors
Interferons are proteins that alter and regulate the transcription of genes within a cell by binding to interferon receptors on the regulated cell's surface and thus prevent viral replication within the cells. There are five types of interferons (IFN), which are designated α (formerly α1), ω (formerly α2), β, γ and τ. Mature human interferons are between 165 and 172 amino acids in length. In humans IFN-α and IFN-ω are encoded by multiple, closely related non-allelic genes. Additionally, there are pseudo-genes of IFN-α and IFN-ω. By contrast, IFN-β and IFN-γ are encoded by unique genes.
The interferons can be grouped into two types. IFN-γ is the sole type II interferon; all others are type I interferons. Type I and type II interferons differ in gene structure (type II interferon genes have three exons, type I one), chromosome location (in humans, type II is located on chromosome-12; the type I interferon genes are linked and on chromosome-9), and the types of tissues where they are produced (type I interferons are synthesized ubiquitously, type II by lymphocytes). Type I interferons competitively inhibit each others binding to cellular receptors, while type II interferon has a distinct receptor. Reviewed by Sen, G. C. & Lengyel, P., 1992, J. Biol. Chem. 267:5017-5020.
Although all type I interferons compete for binding to a common receptor or receptors, the effects of different type I interferons can be different. Pontzer, C. H., 1994, J. Interfer. Res. 14:133-41. Additionally, there appears to be several kinds of type I interferon receptor. For example, there is evidence that the type I interferon receptors of different cell types are different. Benoit, P., 1993, J. Immunol. 150:707. The number of genes encoding the type I interferon receptors is unknown: however, the genes appear to be linked to each other and to at least one gene encoding an IFN-γ receptor component as well. In humans, chromosome region 21q21.1-21.31 encodes all the genes needed for the receptor for type I interferon (Raziuddin, A., 1984, Proc. Natl. Acad. Sci. 81:5504-08; Soh, J., 1993, Proc. Natl. Acad. Sci. 90:8737-41; Soh, J., 1994, J. Biol. Chem. 269:18102-10) and at least one essential component of the type II interferon receptor (Jung, V., 1990, J. Biol. Chem. 265:1827-30).
It is becoming increasingly clear that the interferons have an important role in neuromodulation (Hori, T. et al., 1998, Neuroimmunomodulation 5:172-177; Dafny, N., 1998, Brain Res. Brain Res. Rev. 26:1-15) and neurodegeneracy (Blasko, I. et al., 2001, J. Neuroimmunol. 116:1-4). Of particular relevance is the observation of neuropathology associated with the overproduction of either IFN-α (Akwa, Y. et al., 1998, J. Immunol. 161:5016-5026) or IFN-γ (Corbin, J. G. et al., 1996, Mol Cell Neurosci. 7:354-370) in the transgenic mouse brain. Evidence has been presented in support of a role for IFN-α in neuromodulation (reviewed by Dafney (Dafny, N., 1998, Brain Res Brain Res Rev. 26:1-15)).
The potential role of IFN-γ in neurodegeneracy has only recently been recognized (Blasko, I. et al., 2001, J Neuroimmunol. 116:1-4). Evidence has been presented for a direct role for IFN-γ in neuron apoptosis of neurons in culture (Hallam, D. M. et al., 1998, Neurosci. Lett. 252:17-20) through the induction of neuron caspase activity (Hallam, D. M. et al., 2000, J. Neuroimmunol. 110:66-75).
The Biology of Interferon Action and Down Syndrome
The binding of interferons to their receptor, leads to a cascade post-translational modification to other proteins which are then transported to the nucleus where they regulate the transcription of genes by binding to specific nucleic acid sequences. The nucleic acid sequence which is characteristic of genes responsive to type I interferons is designated the Interferon Sensitive Response Element (ISRE). Reviewed Tanaka, T. & Taniguchi, T., 1992, Adv. Immunol. 52:263. Type-I interferons are synthesized in response to viral infection, except for IFN-τ which is constitutively produced in the placenta; Type II interferons are synthesized in response to antigen stimulation.
Interferons alter the rates of synthesis and the steady state levels of many cellular proteins. An overall effect of interferon is usually an inhibition of cellular proliferation.
The possibility that cells from subjects having Down syndrome may have abnormal responsivity to interferon was introduced by the discovery that a gene encoding an interferon inducible protein, which was subsequently identified as the type I interferon receptor, was located on chromosome-21. Tan Y. H. et al., 1974, J. Exp. Med. 137:317-330. This observation prompted comparisons of the response of diploid and trisomy-21 aneuploid cultured cells to interferon added to the culture medium. These studies have consistently shown an increased responsivity of trisomy-21 cells to interferon. Tan, Y. H. et al., 1974, Science 186:61-63; Maroun, L. E., 1979, J. Biochem. 179:221; Weil, J. et al., 1983, Hum. Genetics 65:108-111; reviewed Epstein, C. J., & Epstein, L. B., 8 LYMPHOKINES pp 277-301 (Academic Press, New York, 1983); Epstein, C. J. et al., 1987, ONCOLOGY AND IMMUNOLOGY OF DOW SYNDROME (Alan R. Liss, 1987). The publications of these studies have been accompanied by speculative conjectures that the altered responsivity to interferon played a role in the pathogenesis of lesions of Down syndrome. See, Maroun, L. E., 1980, J. Theoret. Biol. 86:603-606.
Down Syndrome and Animal Models of It
An animal model of Down syndrome has been constructed by use of the knowledge that human chromosome-21 is syntenic to mouse chromosome-16, i.e., that many of the genes present on each are homologs of each other. Mice having specified trisomies can be bred by use of parental mice having “Robertsonian” chromosomes, i.e., chromosomes that are essentially the centromeric fusion of two different murine chromosomes. A variety of such Robertsonian chromosomes have been identified, including at least two involving chromosome-16 and a second different chromosome: Rb(16.17) and Rb(6.16). Mice homozygous for any Robertsonian or combination of independent Robersonian chromosomes are euploid and fertile.
The intercross (F1) between an Rb(16.17) and an Rb(6.16) mouse is also fully diploid at each genetic locus, although errors in meiosis may cause reduced fertility. Note that in such an F1 both the maternal and paternal chromosome-16 are a part of a Robertsonian chromosome.
Because of meiotic errors the outcross between a mouse having both two different Robertsonian chromosome-16's and a non-Robertsonian mouse gives rise to a trisomy-16 conceptus in between 15% and 20% of cases. Gearhart, J. D. et al., 1986, Brain Res. Bull. 16:789-801; Gropp, A. et al., 1975, Cytogenet. Cell Genet. 14:42-62. The murine trisomy-16 fetuses develop to term but do not live beyond birth by more than a few hours.
Examination of the fetal trisomy-16 and the postpartum human trisomy-21 reveals a number of analogous or parallel lesions. For this reason, the murine trisomy-16 construct is considered to be an animal model of Down syndrome. Epstein, C. J., THE METABOLIC BASIS OF INHERITED DISEASE, 6TH ED. pp 291-326 (McGraw-Hill, New York, 1989); Epstein, C. J. et al., 1985, Ann. N.Y. Acad. Sci. 450:157-168. Because a murine trisomy-16 fetus is not viable post partum, the opportunity to study the neurological pathology of the model has been limited. However, it is clear that in both human trisomy-21 and murine trisomy-16 there is an overall reduction in fetal size and particularly in the development of the fetal brain. Epstein, C. J., THE CONSEQUENCES OF CHROMOSOME IMBALANCE: PRINCIPLES, MECHANISMS AND MODELS (Cambridge University Press, New York, 1986). Further insights into the effects of marine trisomy-16 have been obtained by the formation of Ts16←→2N chimeras (Gearhart, J. D. et al., 1986, Brain Res. Bulletin 16:815-24) and by transplantation of fetal-derived Ts16 tissue into a 2N host (Holtzman, D. M. et al., 1992, Proc. Natl. Acad. Sci. 89:138387; Holtzman, D. M. et al., DOWN SYNDROME AND ALZHEIMER DISEASE, pp 227-44 (Wiley-Liss, New York, 1992).
Alzheimer's Disease and Amyloid Precursor Protein
Alzheimer's disease is a progressive dementia which is characterized by the precipitation of a peptide, termed an A β peptide, of about 40 amino acids within the brain and within the walls of blood vessels in the brain. The A β peptide is derived from the processing of a larger cell surface protein called the β Amyloid Precursor Protein (β APP). Production of the A β peptide is not per se pathological. The functions of both the A β peptide or β APP are unknown.
Several lines of evidence indicate that the deposition of the A β peptide is not merely correlative but rather causative of Alzheimer's disease. The gene encoding β APP is located on chromosome-21 and, as noted above, subjects having Down syndrome develop Alzheimer's disease. More directly, kinship groups have been identified among the many causes of familial Alzheimer's disease in which the inheritance of the Disease is linked to the inheritance of a gene encoding a mutated β APP, moreover the mutation is within the A β peptide itself. Reviewed Selkoe, D. J., 1994, Ann. Rev. Neurosci. 17:489-517. Transgenic mice, having multiple copies of such a mutant β APP gene, operatively linked to a strong, neuronal and glial cell specific promoter, develop the anatomical lesions of Alzheimer's disease at about 6-9 months of age. Games, D. et al., 1995, Nature 373:523.
There is a relationship between Down syndrome and Alzheimer's disease. The gene encoding the β APP is found on chromosome-21. Patients with Down syndrome are at increased risk of developing Alzheimer's disease or Alzheimer's-like pathology, most often by about the fifth decade of life although cases of earlier development have been reported. Mann, D. M. A. et al., 1990, Acta Neuropathol. 80:318-27.
Aids and Inceased IFN Levels
After a latency period that can last for many years, HIV infected individuals “convert” to the immunosuppressed state referred to as “AIDS”. Acquired Immunodeficiency Syndrome (“AIDS”) is a complex of various pathologies that is proceeded by and associated with increased levels of IFN-γ and IFN-α in the blood (Rossel, S. et al., 1989, J. Infectious Diseases 159:815-821) and IFN-α in the CSF (Rho, M B. et al., 1995, Brain, Behavior, and Immunity 9:366-77). Immunization with human IFN-α to reduce IFN levels is associated with the prevention of conversion to AIDS and improved prognosis for AIDS patients (Gringeri, A. et al., 1996, J AIDS and Human Retrovirology 13:55-67) as taught by Zagury, et al. (U.S. Pat. No. 6,093,405). However, this immunization procedure has serious limitations as it is both irreversible and unreliable.
Interferons, like cytokines in the body generally, do not act in the absence of antagonism (Van Weyenbergh, J. et al., 1998, J. Immunol. 161:1568-1574.; Paludan, S. R., 1998, Scand. J. Immunol. 48:459-468.; Ghosh, A. K. et al., 2001, J. Biol. Chem. 276:11041-11048) and/or synergy (Kwon, S. et al., 2001, Nitric Oxide 5:534-546.; Moore, P. E. et al., 2001, J. Appl. Physiol. 91:1467-1474.; Zhang, Y. et al., 2001, J. Interferon Cytokine Res. 21:843-850) caused by other cytokines or other interferon types. Note that some other cytokine combinations have been found to not be synergistic (Czuprynski, C. J. et al., 1992, Antimicrob. Agents Chemother. 36:68-70). In addition, the action of one type of interferon frequently can be mimicked or replaced by the action of another type of interferon (Hughes, T. K. et al., 1987, J Interferon Res. 7:603-614). There is speculation that if you inhibit IFN-γ and IFN-α then disease can be treated (Lachgar, A. et al., 1994, Biomed Pharmacother. 48:73-77, U.S. Pat. No. 5,780,027), however conflicting data in the literature suggests that combined treatment may, in some instances, not be more effective than monotherapy (Lukina, G. V. et al., 1998, Ter. Arkh. 70:32-37).
Presented herein is evidence demonstrating that the pathological negative effects of one type of interferon (IFN-γ) are in the body aided and enhanced in its negative effects by another type of interferon (IFN-α). These data demonstrate that the reduction of interferon bioactivity to relieve a pathological condition can be measurably improved by reducing the activity of both interferon types simultaneously. See, e.g., FIG. 3, which show the results of single vs. double knockout of interferon receptor genes.